A modified homogeneous surface diffusion model for the fixed-bed adsorption of 4,6-DMDBT on Ag–CeOx/TiO2–SiO2

Abstract

The adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel fuel using a fixed bed column was investigated. A modified homogeneous surface diffusion model (HSDM) incorporating a new correlation to describe the “practical” equilibrium adsorption between the moving phase and solid phase was proposed to describe the adsorption kinetics of 4,6-DMDBT adsorption at different operation conditions of flow rate, bed length, adsorbent particle size and influent concentration. A sensitivity analysis indicates that the breakthrough curve is obviously sensitive to the change of the Freundlich constant K values, while film transfer coefficient k_f and surface diffusion coefficient D_s have little effect on the breakthrough curve. The value of the surface diffusion coefficient is 1.76 × 10⁻¹² m² s⁻¹. The axial dispersion coefficient and external mass transfer coefficient are evaluated using empirical correlation. The model equations are solved by the method of lines (MOL). The results prove that the modified HSDM model can predict the fixed bed breakthrough curves well.